Water, flooded over the ground surface of a salt water saturated medium, drains into the ground forming a fresh water zone above the salt water which it displaces. By pumping fresh water from drains spaced at periodic intervals in the fresh water zone, the depth to the saltwater-freshwater interface can be controlled. An analysis is made relating the equilibrium position of the two-fluid interface to the pumping rate, physical properties of the fluids and porous media, the geometry describing the drain location, and the heads of fresh and salt water. An electric analog model is constructed to check the validity of the theoretical analysis.